The present invention relates generally to vapor recovery systems used in conjunction with liquid fuel dispensing equipment for refueling motor vehicles. More particularly, the invention relates to a fuel vapor entrapment device as attached to a fuel dispensing nozzle for assisting fuel vapor recovery during vehicle refueling.
The liquid fuel dispensing equipment found in most common service stations includes a fuel storage tank, a fuel dispenser means, a fuel delivery hose and a fuel dispensing nozzle. During the refueling process, liquid fuel is dispensed from the fuel dispensing nozzle into the vehicle fuel tank causing fuel vapor to be displaced out of the tank and into the atmosphere. Due to environmental concerns associated with such escaping fuel vapor, many governmental bodies require and many suppliers provide fuel vapor recovery systems which collect escaping fuel vapor and deliver the same into a fuel dispensing tank or into a separate vapor recovery tank.
Previous vapor recovery systems incorporated a boot/bellows device which was attached to a fuel dispensing nozzle for collecting escaping fuel vapor and which was in direct communication with a separate fuel vapor recovery line. Such prior art boot/bellows type devices are shown in U.S. Pat. Nos. 3,840,055 (Wostl et al), 3,581,782 (Onufer) and 4,197,883 (Mayer). Such boot/bellows type devices were commonly used in prior art "balanced" vapor recovery systems which relied on the incoming fuel to displace and force the fuel vapors out of the vehicle fuel tank and into and through the vapor recovery system. In a balanced vapor recovery system, a completely closed or sealed equal volume displacement and exchange system is provided for delivering liquid fuel and for capturing and returning fuel vapors to the original fuel dispensing source.
One of the problems associated with the bellows/boot type devices is that they are quite large and cumbersome and generally have a series of predetermined hinge points essential for proper connection to the vehicle fuel tank fill port. Due to the high rate of refueling associated with modern fuel dispensing systems, overfilling and splash back often occurs resulting in fuel becoming trapped in the vapor recovery bellows of prior art boots causing subsequent fuel spillage. The normal fueling operation causes continuous repetitive deflection of the hinge points of the prior art bellows/boot designs. This repetitive hinging action prematurely deteriorates the device and reduces boot service life. As a consequence of the problems associated with closed, balanced systems, open type vapor recovery systems, which do not seal relative to the fuel pipe and which permit the ingestion of outside air during vapor recovery, have become the industry standard. Open systems, as well as some balanced systems, utilize a vacuum generating device to help draw vapor in and through the vapor recovery line.
Balanced systems principally rely on generating a negative pressure at the vapor recovery intake, relative to the pressure in the vehicle fuel tank, by sealing the fuel delivery spout relative to the fuel pipe. The inflow of liquid fuel into the fuel tank creates a positive pressure and displaces the fuel vapors. In balanced systems, vacuum generating devices merely provide assistance in overcoming the loss of pressure associated with long vapor return lines which can cause undesirable pressure build up in the automobile fuel tank. Unlike balanced systems, the vacuum generating devices of open systems generally provide negative pressure at the vapor recovery intake. The open system derives its name from the fact that no seal is required between the nozzle spout and the vehicle fuel pipe. Accordingly, no "donut" seal or "bellows" type boot is required for the effective operation of an open system. Because no seal is used, open vapor recovery systems may draw in ambient air into the vapor return line during vapor recovery.
While the present invention provides beneficial use in balanced systems, such as disclosed in U.S. Pat. No. 4,166,485(Wokas), it is particularly useful in vacuum-assisted fuel vapor recovery systems. In such vacuum-assisted systems, a motor operated vacuum pump is placed in the fuel vapor recovery line so as to actively draw in escaping fuel vapor into the recovery line during vehicle fuel tank refueling. To enhance vacuum-assisted vapor recovery system operation, a device is needed to "trap" or contain the escaping vapors and limit the amount of outside air ingested into the vapor recovery system during the refueling process.